science

Transitive dependency

Transitive dependency is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Transitive dependency rather than just read about it. In short: A transitive dependency is an indirect dependency relationship between software components. This kind of dependency is held by virtue of a transitive relation from a component that the software depends on directly.

Key takeaways

Transitive dependency belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Transitive dependency to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Transitive dependency from memory before moving on to harder problems.

Reference excerpt

A transitive dependency is an indirect dependency relationship between software components. This kind of dependency is held by virtue of a transitive relation from a component that the software depends on directly.

Computer programs In a computer program a direct dependency is functionality from a library, or API, or any software component that is referenced directly by the program itself. A transitive dependency is any dependency induced by a different component, that in turn is directly or indirectly referenced by the program. E.g. a call to a log() function may induce a transitive dependency to a library that manages the I/O of writing a message to a log file. Dependencies and transitive dependencies can be resolved at different times, depending on how the computer program is assembled and/or executed: e.g. a compiler can have a link phase where the dependencies are resolved. Sometimes the build system even allows management of the transitive dependencies. Similarly, when a computer uses services, a computer program can depend on a service that should be started before to execute the program. A transitive dependency in such case is any other service that the service we depend directly on depends on, e.g. a web browser depends on a Domain Name Resolution service to convert a web URL in an IP address; the DNS will depend on a networking service to access a remote name server. The Linux boot system systemd is based on a set of configurations that declare the dependencies of the modules to be started: at boot time systemd analyzes all the transitive dependencies to decide the execution order of each module to start.

Database management systems

Suppose entities A, B, and C exist such that the following statements hold:

A → B direct dependency relationship exists. There is no B → A relationship. B → C direct dependency relationship exists. Then the functional dependency A → C is a transitive dependency (which follows the axiom of transitivity). In database normalization of relational databases, one of the important features of third normal form is that it excludes certain types of transitive dependencies. E.F. Codd, the inventor of the relational model, introduced the concepts of transitive dependence and third normal form in 1971.

Example A transitive dependency occurs in the following relation:

The functional dependency {Book} → {Author nationality} emerges; that is, if we know the book, we can know the author's nationality. Furthermore:

{Book} → {Author} {Author} does not → {Book} {Author} → {Author nationality} Therefore {Book} → {Author nationality} is a transitive dependency.

Notes

Illustrations

Worked examples

Example 1 — a first encounter with Transitive dependency

Start with the simplest possible case. Write down what Transitive dependency claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Transitive dependency before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Transitive dependency ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Transitive dependency

In research: Transitive dependency appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Transitive dependency in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Transitive dependency is common in secondary-school and first-year university syllabi. It links to neighbouring topics Database constraints, Database theory, so understanding it makes those chapters shorter.
In everyday life: Look for Transitive dependency outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Transitive dependency in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Transitive dependency means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Transitive dependency out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Transitive dependency in simple terms?

Why does Transitive dependency matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Transitive dependency?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Transitive dependency.